If I understand you correctly, you want to award the badge based on comments that fulfills these requirement
- Answers the question
- More well-received (i.e. more up-votes) than the highest voted answer
Requirement #2 is relatively easy to check (I think).
Requirement #1 is more troublesome for the system. I mean, it's easy for us (humans, unicorns, doorknobs, and anime characters) to distinguish between
- comments that is an answer to the question, and
- comments that is a feedback to a question (request for clarification; statement that the issue is not reproducible, etc.)
but the system can't†.
Let's say we have a feedback-type comment that has a higher upvote than the highest-voted answer, that's like comparing apples and oranges – then that's not a meaningful comparison, at least in my book.
And even in the case of meaningful comparison (i.e. comparing answer-type comment and answer), there is also the issue of encouraging "just do this" type of answer vs in-depth, detailed answers (as many has mentioned).
† Unless we add new features to mark a comment as an answer or a feedback – more trouble than it's worth